/**
 * Definition for singly-linked list.
 * function ListNode(val) {
 *     this.val = val;
 *     this.next = null;
 * }
 */
/**
 * @param {ListNode} l1
 * @param {ListNode} l2
 * @return {ListNode}
 */
 var mergeTwoLists = function(l1, l2) {
    let reshead=new ListNode(0);
    let p=reshead;
    while(l1 && l2){
        if(l1.val<l2.val){
            p.next=l1;
            l1=l1.next;
            p=p.next;
        }
        else{
            p.next=l2;
            l2=l2.next;
            p=p.next;
        }
    }
    if(l1){
        p.next=l1;
    }
    if(l2){
        p.next=l2;
    }
    return reshead.next;
};